An analysis of the relationship between the IMF section boundary crossing, solar flares, the sunspot 11 year cycle variation and the thunderstorm index is given, using the superposition epoch method, for data from more than 13,000 thunderstorms from 10 meteorological stations in the Beijing area and the Northeast region during 1957 to 1978. The results show that for some years a correlation exists between the thunderstorm index and the positive IMF section boundary crossing. The thunderstorm index increases obviously within three days near the crossing and on the seventh day after the crossing. The influence of the crossing on thunderstorms is stronger in the first half year than the latter half year. For different classes of solar flares, the influences are not equally obvious. The solar flares which appeared on the west side, especially in the western region (from 0 to 30 deg) have the most obvious influence. There is no discernible correlation between the thunderstorm index and the sunspot eleven-year cycle.